A brush fire Friday near San Bernardino, Calif., prompted evacuations and caused backups of nearly 30 miles each way on Interstate 15, the vital freeway that connects Los Angeles and Las Vegas, Nev., officials said.

“This is one of the busiest travels days of the year,” said Capt. Josh Wilkins of the San Bernardino County Fire Department, referring to the Labor Day holiday.

Officials are urging motorists to stay away from I-15.

Northbound lanes were reopened Friday evening in Cajon Pass near State 138, between Victorville and San Bernardino, Wilkins said. Southbound lanes were closed; officials said they could possibly reopen late Friday or overnight.

The fire had burned about 1,110 acres by Friday evening.

“We’re saving houses,” Wilkins said, while adding 20 percent of the blaze is considered contained.

Residents of about 1,500 homes in the Oaks Hill community have been evacuated, Wilkins added. Two firefighters suffered undisclosed injuries. One incident was thought to be heat-related.

Wind gusts were affecting the firefighting efforts.

“Cajon Pass is a geographic funnel,” Wilkins told CNN.

Seven helicopters and 14 fixed-wing aircraft have been called in to help 750 firefighters on the ground, Wilkins said.

The cause of the fire has not been determined.

CNN’s Carey Bodenheimer, Phil Gast and Sonya Hamasaki contributed to this report.